Using supercomputers to study COVID in classrooms

Scientists at the US Department of Energy’s (DOE’s) Argonne National Laboratory (Argonne) are using supercomputers to study how aerosol viral particles are distributed in a ventilated classroom.

The research is being used to determine optimal placement of HVAC outlets to minimise “dead zones” and maximise ventilation and therefore improve indoor air quality (IAQ).

Using the Summit, the fastest supercomputer in the US, the team simulated the spread of aerosols through a model elementary school classroom layout to determine the best types of ventilation for such spaces. Led by Rao Kotamarthi, the team wanted to understand how social distancing requirements affect disease transmission indoors.

The traditional arrangement of the ventilation pathway in a classroom places the HVAC outlet and the classroom door on opposite walls. The researchers, however, found this created dead zones.

As the name suggests, dead zones are areas in which the air velocities are so low that aerosol particles released during normal breathing and speaking tend to linger in these regions and are not expelled via ventilation.

The researchers found that placing the HVAC inlet and the door on the same wall considerably reduces the extent of these dead zones.

“Through these simulations, we found that if we use the same air conditioning with the same blowing rate, the same velocity, and the same temperature gradient, but we put the door and HVAC inlet on the same wall, it reduces the formation of the dead zone significantly,” says Argonne computational scientist Ramesh Balakrishnan.

The results provide engineers with information about the ideal design and placement of HVAC systems in classrooms, which could help mitigate the spread of COVID-19 and other viruses in enclosed spaces. They could also help scientists understand the effects of social distancing on the transmission and distribution of aerosols in indoor environments.

The Argonne team ran large eddy simulations (LES) on the Oak Ridge Leadership Computing Facility’s (OLCF’s) Summit supercomputer. The team simulated turbulent flows – the unsteady movement of gases and fluids – with a distribution of aerosol particles ranging in size from 0.1 to 5 microns. They simulated these flows in a classroom a size of 14m × 12m × 3m.

The study modelled cannister ventilation, in which an HVAC vent is mounted high up on the wall and blowing air horizontally into a room. The researchers wanted to understand the best possible way to mount the HVAC units and the air temperature needed to keep people in the room comfortable and safe.

Using various scenarios of room and desk configurations, the team discovered that warm air creates bigger dead zones than cool air. This was due to the formation of a thermal stratification layer that suppresses turbulence, thereby increasing the extent and duration of the dead zone.

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